1. Field of the Invention
The present invention relates to a photopolymer elastomeric article which is designed to be used primarily in a flexographic printing system. Flexographic printing is a method of rotary letterpress printing which employs flexible elastomer printing plates. In this system the ink is transferred directly from the raised surfaces of the elastomeric plate to the printing stock.
Flexible photopolymer printing plates of the present invention comprise three elements:
1. An elastomeric polymer matrix, PA0 2. A photopolymerizable, ethylenically unsaturated crosslinking agent, as typified by esters of acrylic or methacrylic acid and PA0 3. A photoinitiator, which is a compound, which when irradiated, will initiate polymerization and/or crosslinking.
The chemical nature of these three elements may be varied and additional components added as needed to improve plate production and performance characteristics, especially printing quality. The ability of the polymer matrix to accept such additives is of great advantage as photopolymer plates are being used in many different types of printing requiring distinctly different properties. Those properties most desirable in flexible photopolymer plates include solvent resistance, wide choice of durometer (hardness), short plate processing time, resistance to cracking, and resistance to postcuring. The current invention combines more of these desirable qualities than any in the prior art, and involves the use of a chlorosulfonated polyethylene or blends thereof as the polymer matrix.
2. Description of the Prior Art
U.S. Pat. No. 2,760,863 discloses a process to make relief images from a photopolymerizable system containing a polymeric thickener or filler, an addition polymerizable monomer, and a photopolymerization initiator.
U.S. Pat. No. 3,024,180 and Canadian 614,181 disclose relief plates based on polymers of 1,3-butadiene and halogen-substituted 1,3-butadiene, and mentions copolymers thereof, with aryl olefins, e.g. styrene, acrylic esters and nitriles.
U.S. Pat. No. 3,674,486 discloses printing plate compositions based on block copolymers of styrene and polybutadiene (SBS) or polyisoprene (SIS).
U.S. Pat. No. 3,764,324 discloses a printing plate formulation consisting of an unsaturated polymer including butadiene or acrylonitrile, and a saturated polymer including butadiene or acrylonitrile, and a saturated halogenated polymer, such as polyvinylchloride, which result in a hard, solvent resistant plate.
None of these references disclose a flexible photopolymer plate in which the polymer matrix is chlorosulfonated polyethylene.